Non-volatile memory devices retain stored data even when disconnected from power. Examples of non-volatile memory devices include NAND flash memory, NOR flash memory, phase change memory (PCM), and resistive random-access memory (RRAM). Different data stored in the non-volatile memory may correspond to different threshold voltage (Vt) or different resistance of the memory cell. The memory state may thus be detected by sensing the current flowing through the memory cell. As the number of memory cells in a memory chip increases, there is a need for a cost-effective and reliable sensing circuit and sensing method for a non-volatile memory device.